flow.size: 6
row.1: 8,0,0,0,0,0
row.2: 6,0,6,4,1,0
row.3: 0,0,0,0,0,0
row.4: 0,0,3,1,0,0
row.5: 4,3,2,0,2,0
row.6: 8,0,0,0,0,0

